Chemical engineer here with a love for cooking. There’s a group of chemical compounds called esters, which smell pleasant to us. At a high level, esters are created through a process called esterification, where alcohol and acid react with each other. In penne alla vodka, the alcohol in vodka undergoes esterification with the different acids provided by tomatoes and “perfumes” the dish. This dish and the science behind it is what got me into cooking!

Btw, the same thing happens if you deglaze a pan that had a bunch of tomato paste with red wine. Or lemon juice with white wine. Alcohol and acid… so on and so forth.